Mixing synthetic and mineral oil

[Nick_H]

I need to top up the oil in the genny, and I'm not sure if the service engineer used mineral or synthetic oil (I specified synthetic, but there's only mineral oil shown on the bill, and I can't contact the specific engineer, and the company don't seem sure)

Is it "safe" to add either mineral or synthetic to the other in small quantities, or is there any easy way of telling which type of oil it is.

 

[DAKA]

unless there is zero oil showing on the dip there is no need to do anything except monitor the level to check its not still going down.

Then contact when you can.

Chances are its mineral or you would have noticed the price on the bill in which case you can add either mineral or semi synthetic.

If there isnt any oil showing and there isnt any in your bilges then chances are he has forgotten to add oil at all in which case you are safe to add either.

Is it an easy job to empty the remaining oil out ? some gennies have pumps permanently attached .

 

[rafiki_]

Latestarter is probably the expert on this, but I think you are ok mixing the oils.

 

[Wiggo]

If in any doubt, use semi-synthetic. Semi will play nicely with either mineral or fully synthetic, but you shouldn't mix mineral and fully synthetic...

 

[Nick_H]

thanks all, i'll monitor the level closely, and if no conflicting advice in the meantime top up with semi-synth if necessary

 

[[2068]]

There should be no problem mixing mineral with synthetic, assuming that the synthetic is a mineral-derived automotive oil. All you are doing is producing your own "semi synthetic".

http://www.carbibles.com/engineoil_bible.html

The ones that don't mix are the pure synthetics you might find in a gearbox.

 

[stuhaynes]

Don't do it, change the oil. Oil seals are designed for either synthetic or mineral. If I remember correctly mineral oil in a synthetic system will rot the oil seals. Expensive repair. Drain the oil asap and make sure the oil is correct. It's not worth risking your engine.

 

[rafiki_]

Don't do it, change the oil. Oil seals are designed for either synthetic or mineral. If I remember correctly mineral oil in a synthetic system will rot the oil seals. Expensive repair. Drain the oil asap and make sure the oil is correct. It's not worth risking your engine.

First I've heard of this. You can use either synth or mineral oils in my car engine. Only difference is the mineral does not have the temp range or durability as an oil. Neither will effect the seals. In my Merc diesels, Merc recommends the mineral oil as it is so much cheaper, and the engines were designed before synth oils were widespread, and so no real benefit.

 

[penfold]

First I've heard of this. You can use either synth or mineral oils in my car engine. Only difference is the mineral does not have the temp range or durability as an oil. Neither will effect the seals. In my Merc diesels, Merc recommends the mineral oil as it is so much cheaper, and the engines were designed before synth oils were widespread, and so no real benefit.

You haven't heard it before because it's not true.

 

[Latestarter1]

I need to top up the oil in the genny, and I'm not sure if the service engineer used mineral or synthetic oil (I specified synthetic, but there's only mineral oil shown on the bill, and I can't contact the specific engineer, and the company don't seem sure)

Is it "safe" to add either mineral or synthetic to the other in small quantities, or is there any easy way of telling which type of oil it is.

You have not mentioned make and type of genny.

Another question, why did you specify a synthetic lube and what grade?

Did you refer to manufacturers lube oil guidelines?

Most wee Japanese industrial engines were never designed for synthetic lubes as they have rasonably high top ring temperatures, at best synthetic does absolutely nothing for you at worst dependant on what grade lube you have specified could cause a number of issues.

Yanmar USA expessly prohibit use of anything other than mineral lube to 15W40 or 10W10 for operation below zero ambients.

Kubota use mineral 15W40 CH-4 for first factory fill in many applications.

Service guys involved with small industrial engines also run scared of synthetic lubes because they generally have a cost factor of x 3 over mineral lubes thare is always the drive to extend lube drains to make the cost/benifit stack up, it is then that the trouble really starts.

If manufacturers specified lube/ service interval gives optimum engine life why do anything different, the guys who designed the engine know best.

It is likely that service tech knows about the type of genny motor and just assumed your instructions were incorrect. If mineral oil and grade is specified on the invoice then top up with that if you really have to..........Do not mix viscosities and and or base stock types.

More questions, suprised you need to top up............How may hours has your genny run since it was serviced?? Generally little Japanese industrial motors have extremely good oil control, unless your units has been running with squat all loading and started glazing the bores. Also do you run motor on the high dip stick mark?? Very common for boat owners to be over zelious with lube oil top ups and engine will want to burn off excess lube, staying between the two marks can reduce top ups.

If you are hitting lube consumption issues act now.....Fire up genny and stick everything on load it up as much as you can and give it at least three hours of torture.

Good luck

 

[Tugw]

You haven't heard it before because it's not true.

Come and have a look at one of our compressors,The result of mixing oils,its going to cost a bleedin fortune to put right,But then again what do Siemens know about it?

 

[lynall]

Gets mixed all the time in my job doesnt cause any issues, this is in engines not compressors.
Put simple syn goes longer between changes, add mineral to syn oil and you have downgraded the whole oil to mineral intervals, ie shortened it.
I realise theres loads of other differences but thats in in a nutshell really.


Lynall

 

[DAKA]

If in any doubt, use semi-synthetic. Semi will play nicely with either mineral or fully synthetic, but you shouldn't mix mineral and fully synthetic...

Semi-synthetic isnt usually a 50% 50% mix of mineral and synthetic oil.

If anyone bothers to check whats actually in the tin marked semi-synthetic they will usually find

Mineral oil 99%
Anti-froth additive
Anti-sludge additive
Alkaline (to deal with acidic deposits, extends oil life)
adhesive (for the want of a better word to help stick the oil to higher parts of the engine to reduce start up wear).


Manufacturers feel the addition of these additives allows the use of the term semi-synthetic and a special numpty price load .

 

[Latestarter1]

Gets mixed all the time in my job doesnt cause any issues, this is in engines not compressors.
Put simple syn goes longer between changes, add mineral to syn oil and you have downgraded the whole oil to mineral intervals, ie shortened it.
I realise theres loads of other differences but thats in in a nutshell really.


Lynall

Oil drain intervals have been established field trail progams you cite the issue exactly, using synthetic lubes results in pushing out manufacturers lube drains and ignoring the very data generated during the engine design process. Often results in shortening life of the motor.

Why? Many automotive synthetic lubes are low SAPS which stands for (sulphur and phosphorus) it may be very good oil for vehcles equipped with a cat or DPF by reducing ash and sustain exellent viscocity, but there extreme pressure properties are questionable in engines with simple mushroom tappets in valve train. Low SAPS lubes have very low levels of ZDDP (zinc di-alkyl di-thio phosphate) to improve catalyst life.

Modern LDA (automotive) diesel engines are generally overhead camshaft with roller tappets and low Hertz stress designed into critical valve train components. Whilst low SAPS lubs have many other sexy additives to make up for the loss of ZDDP you simply cannot ignore the fact that ZDDP and mushroom tappets found in simple industrial engines are real comfortable bed fellows.

 

[penfold]

Come and have a look at one of our compressors,The result of mixing oils,its going to cost a bleedin fortune to put right,But then again what do Siemens know about it?

The post I was referring to mentioned misuse of synth or mixing of synth and nonsynth attacking seals in diesel engines; I have never heard of this happening. Googling reveals nothing; this suggests it doesn't happen.

Compressors have a completely different set of lubrication requirements to diesels, putting the wrong oil in one can destroy them and possibly cause fire and explosion. It's also not very relevent to this thread beyond illustrating what can happen when you mix two incompatible oils.

 

[Nick_H]

I've now had it confirmed by the engineer, and in usual SoF style they completely ignored my instruction to use synthetic and just put in what they had lying around, BP Vanellus Multi-fleet 15W40, which appears to be a run-of-the-mill mineral oil, so i've topped up with some semi-synth which I have on board based on advice above.

Thanks again to all for replies

 

[jimbaerselman]

Slight oversimplification follows -

In choosing an oil, only two things matter. (1) what it's going to be used for and (2) the environmental temperatures likely.

The API or ACEA spec defines the first (includes type of engine, with tweaks if catalysts are used) and the 10-30 number defines viscosity - the second.

How the specification is achieved is irrelevant. Mineral oil, vegetable oil, synthetics - any could be used interchangebly, or mixed, as long as they meet the spec. So purchase the spec which the machine manufacturer quotes, and ignore brands or descriptions.

Brand management deliberately fogs the issue, by saying such things as "never mix our (perfect) oil with other (poor imitation) oils or you'll miss the unique benefits of <select whichever bulls**t quote suits them>".

 

[Latestarter1]

I've now had it confirmed by the engineer, and in usual SoF style they completely ignored my instruction to use synthetic and just put in what they had lying around, BP Vanellus Multi-fleet 15W40, which appears to be a run-of-the-mill mineral oil

Cor talk about damm with faint praise!

If you have a small Japanese industrial engine BP Vanellus Multi-fleet 15W40 is perfect for the engine and give you ultimate protection.

I note that you have not bothered to answer any questions regarding your application.

In your original post you talked about topping up with a synthetic lube no viscosity given, now switched gears to to say that topping up with a hydrocracked mineral lube.

No wonder guys servicing took little notice of your instructions................

 

[penfold]

If you have a small Japanese industrial engine BP Vanellus Multi-fleet 15W40 is perfect for the engine and give you ultimate protection.

Going by the vessel in the OP's profile, it will be a single phase genny of perhaps 20KVA, so more or less as you describe.

 

[Davegriff]

From my days working for Shell, I always understood mixing synthetic with mineral oil does no harm at all. Done it loads of times. Don't know why you'd want to put expensive synthetic in a relatively low tech genny though.